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21.
Moiseev S.N. Filin S.A. Kondakov M.S. Garmonov A.V. Savinkov A.Y. Yun Sang Park Do Hyon Yim Jae Ho Lee Seok Ho Cheon Ki Tae Han 《Communications Letters, IEEE》2006,10(8):620-622
In this letter we introduce our system load model for the orthogonal frequency division multiple access (OFDMA) network. We formulate the requirements to the system load model and present its definition. The system load model comprises the uplink load, the downlink load, the sector load, and the network load. We describe our approach to combine the time-frequency and power shared system resources in the OFDMA network. 相似文献
22.
Shang Hyon Shin 《Journal of Mechanical Science and Technology》2002,16(6):757-761
When a layer of cylindrical composite component containing an axisymmetric residual stress state is removed from the inner
or outer surface, the dimension of the remaining material changes to balance internal forces. Therefore, in order to machine
cylindrical composite components within tolerances, it is important to know dimensional changes caused by residual stress
redistribution in the body. In this study, analytical solutions for dimensional changes and the redistribution of residual
stresses due to the layer removal from a residually stressed cylindrically orthotropic cylinder were developed. The cylinder
was assumed to have axisymmetric radial, tangential and axial residual stresses. The result of this study is useful in cases
where the initial residual stress distribution in the component has been measured by a non-destructive technique such as neutron
diffraction with no information on the effect of layer removal operation on the dimensional changes. 相似文献
23.
In observing the stereoscopic display at the viewing distance of 1 m, the amount of the perceived depth was determined by the positions of the crossing point that the viewing direction of two eyes intersect. The positions of the crossing points of stereoscopic stimuli were controlled, and the accommodation was measured by the autorefractometer for the seven participants. Accommodation was also measured when viewing the real film chart which was placed at the same position as these crossing points. The accommodation change when viewing the stereoscopic display was measured to be noticeable only when the crossing point was quite near the participant, but this change was still much smaller compared with the accommodation change when viewing the real film chart. This change in accommodation implies the possible occurrence of fatigue related to the accommodation–convergence conflict, while the constant accommodation within the range of DOF implies no conflict between the accommodation and convergence. This measurement scheme may be used to define the range of DOF where the accommodation remains little changed, and thus define the depth of the 3D object at which no accommodation–convergence conflict occurs, for a given stereoscopic display. 相似文献
24.
Jae Sung Lee Hwan Kwang Lee Je Young Kim Suong‐Hyu Hyon Sung Chul Kim 《应用聚合物科学杂志》2003,88(9):2224-2232
Thermally induced phase separation in poly(lactic acid)/dialkyl phthalate systems was investigated. Poly(DL ‐lactic acid) (PDLLA) and poly(L ‐lactic acid) (PLLA) with different molecular weights were used. A series of dialkyl phthalates, with different numbers of carbon atoms in the alkyl chain, were employed as solvents to control the interaction between polymer and solvent. The liquid–liquid phase‐separation temperature of the poly(lactic acid) solutions decreased systematically with a shorter alkyl chain in the phthalate. Based on the interaction between polymer and solvent and the molecular weight of polymer influencing liquid–liquid phase‐separation temperature significantly but crystallization temperature only slightly, proper thermal conditions were employed to investigate competitive phase separation and crystallization in PLLA solutions. Factors that can influence the final morphology of PLLA solutions were examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2224–2232, 2003 相似文献
25.
Jin Goo Lee Myung Geun Park Hyon Hee Yoon Yong Gun Shul 《Journal of Electroceramics》2013,31(1-2):231-237
Yttria-doped bismuth (YDB) and gadolinia-doped ceria (GDC) are investigated as a bilayer electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). LSM-YDB is used as a cathode material in order to improve the poor ionic conduction of LSM and the compatibility with the YDB electrolyte. The performance of the bilayer cell was measured under humidified H2 (3 % H2O) atmosphere and an operating temperature between 500 °C and 650 °C. The polarization resistance and ohmic resistance of the GDC-YDB bilayer cell were 0.189 Ωcm2 and 0.227 Ωcm2 at 650 °C, respectively. The bilayer cell showed 0.527 Wcm?2 in the maximum power density at 650 °C, which is about two times higher than the single-layer cell of 0.21 Wcm?2. The OCV of the bilayer cell was 0.89 V at 650 °C, suggesting that the electronic conduction caused by the reduction of ceria was successfully suppressed by the YDB layer. The introduction of an YDB-GDC bilayer cell with LSM-YDB cathode thus appears to be a promising method for improving the performance of GDC-based SOFCs and reducing operating temperature. 相似文献
26.
Kyung Sun Park Jangmi Baek Yoonkyung Park Lynn Lee Jinho Hyon Yong‐Eun Koo Lee Nabeen K. Shrestha Youngjong Kang Myung Mo Sung 《Advanced materials (Deerfield Beach, Fla.)》2017,29(6)
Manufacturing high‐performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high‐performance organic electronic and optoelectronic devices relies on high‐quality single crystals that show optimal intrinsic charge‐transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high‐performance organic integrated electronics are also addressed. 相似文献
27.
Kang HC Stephenson GB Liu C Conley R Khachatryan R Wieczorek M Macrander AT Yan H Maser J Hiller J Koritala R 《The Review of scientific instruments》2007,78(4):046103
We report a process to fabricate multilayer Laue lenses (MLL's) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL's are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5 keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL's. 相似文献
28.
Hyon Hee Yoon 《Korean Journal of Chemical Engineering》1998,15(6):631-636
A two-stage biomass pretreatment process-a combination of autohydrolysis and aqueous ammonia percolation-was experimentally
studied as a method to remove and recover hemicellulose from lignocellulosic biomass. Hemicellulose was completely separated
from the biomass after 1 hr of autohydrolysis at 200‡C. As reaction temperature and/or time of autohydrolysis was increased
in the range of 170-200‡C and 1–2.5 hr, respectively, the amount of hemicellulose solubilization was increased ; however,
more sugars were decomposed. Most of the extracted hemicellulose was recovered as xylose oligomer. Hemicellulose was found
to inhibit the enzymatic hydrolysis of cellulose. When the biomass was consecutively pretreated with pure water at 180‡C for
30 min and with 10 wt% ammonia solution at 180‡C for 30 min, about 62% of the hemicellulose was extracted. The enzymatic digestibility
of the pretreated biomass was as high as 95 %. 相似文献
29.
Low-temperature gelation of poly(vinyl alcohol) (PVA) solution was performed in the presence of CaCl2. The resulting PVA hydrogels showed high stickiness and excellent water-holding ability. These properties became more remarkable with increasing CaCl2 concentration in solvent. Furthermore, both the peel strength on stainless steel and the degree of swelling of the PVA hydrogel drastically increased as CaCl2 concentration was increased from 20 to 30 wt %. It is concluded that the sticky and water-holding properties of PVA hydrogels are intimately related to the state of hydration of Ca ions in aqueous environment. © 1993 John Wiley & Sons, Inc. 相似文献
30.
In future wireless systems, the coverage of a base station will decrease due to the characteristics of the channel at high-frequency
bands. To expand the service coverage, a hybrid network that combines an ad hoc network with a cellular (or wireless LAN)
network, appears to have great potential. In such systems, some mobile users outside the service area can access the network
with the aid of other intermediate mobiles. However, this method incurs energy consumption in routing users, which could be
a serious obstacle for wide-spread deployment of multihop wireless networks. Therefore we consider a revenue-cost model and
propose a profit-based routing strategy that encourages routing users to actively participate in the relaying service because
they are compensated for their energy consumption cost. Our strategy enables each mobile node to find an appropriate multihop
path to a base station (or access point) that satisfies the interests of the service provider and the users. Numerical results
show that our model successfully expands the network coverage area while ensuring the profit of each system involved. 相似文献